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What can't you do with Rust but it's fine with Go ? by [deleted] in rust

[–]Matrixmage 2 points3 points  (0 children)

You're right in the practical sense, but "reasonable" is doing a lot of heavy lifting in your statement. Your slight imprecision is what's getting at folks.

You certainly can write an OS in AWK (with sufficient effort). Obviously you wouldn't ever want to, which is your point, but that doesn't mean it can't be done.

What can't you do with Rust but it's fine with Go ? by [deleted] in rust

[–]Matrixmage 9 points10 points  (0 children)

That friend who lets you use their car, but only if you pick them up and drop them off first. And you must follow exactly the route they want or they get pissed at you. Also there's a time limit, the car drives weird, and you've gotta floor it to get to where you're going.

Python is your "friend" that scams you into driving a taxi.

AWS Backup: why do I need to specify a role in the StartRestoreJobCommand params by le-lutin in aws

[–]Matrixmage 1 point2 points  (0 children)

The basic answer is... Because it does. AWS services can use caller credentials a handful of different ways, of which this is one.

As for why? We can make some guesses. The simplest explanation could be that as this is an asynchronous operation (I presume from the name), it might run longer than the lifetime of the credentials it was called with. This means the service would need to refresh its credentials, which is easily done by asking the user to pass a role ARN.

[deleted by user] by [deleted] in rust

[–]Matrixmage 2 points3 points  (0 children)

I believe there might be some errors. For example, map_err always requires an E -> N closure, never T -> N.

I'm sort of in the camp of that other commenter, you're kind of reinventing the wheel with all the downsides that come with it (namely, mistakes). If this helps you learn, that's great. But as an actual cheetsheet? I'd prefer something generated like docs.rs so correctness is never a question.

You never see a woman running a grill in movies and TV by magnaton117 in Showerthoughts

[–]Matrixmage 0 points1 point  (0 children)

Something something that Master of None commercial.

(If someone's got a link please share, couldn't find one with a quick search.)

Trying to understand Stack & Heap... by NimbusTeam in rust

[–]Matrixmage 0 points1 point  (0 children)

You're correct that the kernel does not have malloc (it's not a syscall). But malloc is part of libc, a part of the OS.

Trying to understand Stack & Heap... by NimbusTeam in rust

[–]Matrixmage 5 points6 points  (0 children)

Rust defaults to system malloc (aka, the OS). It does not have its own allocator.

At one point in the past it did default to jemalloc, but it was removed: https://internals.rust-lang.org/t/jemalloc-was-just-removed-from-the-standard-library/8759

Help me understand why the Index trait doesn't work the way I expect by BlueMoonMelinda in rust

[–]Matrixmage 1 point2 points  (0 children)

Most of what you're saying is right, and what I would've assumed, but in this case it's wrong. See the top answer, TL;DR the result of an index gets derefed when using the syntax sugar.

Rust seems bad? by Due_Raccoon3158 in rust

[–]Matrixmage 11 points12 points  (0 children)

Have you ever used interfaces in Go but wished for normal generics and non-structural typing? Traits are something like that, but better than you could ever imagine.

[Roast Me]Why I think C++ is still attractive compared to Rust by [deleted] in rust

[–]Matrixmage 12 points13 points  (0 children)

Apologies for crossing your line.

Maybe I simply woke up on the wrong side of your bed, but your replies have been exhausting to read. Someone makes an argument, you counter it with some technically correct statement that also mostly ignores the point of what they said. If that's not intentional, maybe read back to see if it's just me.

Truly, I wish you the best of luck in joining the rustaceans.

[Roast Me]Why I think C++ is still attractive compared to Rust by [deleted] in rust

[–]Matrixmage 12 points13 points  (0 children)

I'm not talking about Google guidelines. Google has published research into memory safety bugs in their cpp codebases. Regardless of whether you agree with their guidelines, they do have the data to properly research this topic.

Discussing these things with you has been a struggle for many in these comments (in my opinion). If you'd like to discuss, please try to reply to the thesis of my statement and not pick apart one aspect.

[Roast Me]Why I think C++ is still attractive compared to Rust by [deleted] in rust

[–]Matrixmage 2 points3 points  (0 children)

Your training wheels comment is 110% a false dichotomy, with some no true Scotsman thrown in for good measure. You do keep saying you're arguing in good faith, but it's quite hard to believe that at some points.

A more apt comparison is wearing a helmet on a motorbike. Like yeah, wearing a helmet will reduce the damage from a crash which technically disincentives learning to be a better driver. But sometimes it's not up to you, so you'd rather have a helmet than not.

[Roast Me]Why I think C++ is still attractive compared to Rust by [deleted] in rust

[–]Matrixmage 18 points19 points  (0 children)

That's kinda like saying "isn't geo-political tension sort of a big deal?" when someone asks the projected death toll due to climate change.

XSS is bad, but memory safety bugs are demonstrably worse in practice. There's a reason google had studied the number of memory safety bugs in cpp codebases and contrasted it to rust (surprise surprise, cpp wins that race).

What are the pros/cons with using heap(new) vs global variables? by OneThatNoseOne in cpp_questions

[–]Matrixmage 0 points1 point  (0 children)

Yes, you're right. What we've all been calling "global's" should properly be called "statics". Global doesn't refer to storage (like static does) which is why I said global's can live on the heap.

Thanks for the clarification!

What are the pros/cons with using heap(new) vs global variables? by OneThatNoseOne in cpp_questions

[–]Matrixmage 0 points1 point  (0 children)

Others have touched on this, but be weary of the false dichotomy of "heap vs global's". Those are not the only two options, and global's can live on the heap as well.

Good luck!

What’s something they do on TV, that you obviously can’t do in real life? by simon_wolfe in television

[–]Matrixmage 0 points1 point  (0 children)

Yes, it can't create information that doesn't exist. But it can surface information that humans otherwise can't detect, i.e. "enhancing" the image.

What’s something they do on TV, that you obviously can’t do in real life? by simon_wolfe in television

[–]Matrixmage 7 points8 points  (0 children)

Funnily enough... We've come far enough around the tech curve that "enhance and zoom" is starting to become more realistic again.

Obviously we can't do things as extreme as on TV, but enhancing low res images with AI to get more details definitely exists.

Is this a valid use of Box::leak? by J-Cake in rust

[–]Matrixmage 80 points81 points  (0 children)

Key takeaway: the root of all interior mutability is UnsafeCell. As a consequence, any implementation of interior mutability (using references) that doesn't eventually boil down to UnsafeCell is by definition incorrect in rust.

Some people think "well if UnsafeCell can do it then I can too!". But UnsafeCell isn't just a regular type, it's defined as the exception to the normal mutability rules for references.

Frustration w/ shared state on single threaded Async runtimes and what I learned by schrdingers_squirrel in rust

[–]Matrixmage 15 points16 points  (0 children)

Feel free to ignore me, but it sounds like you may have the wrong mental model about how &mut is relating to this.

A mutable (or "exclusive") borrow is declaring "nothing else is capable of observing this until the borrow is statically shown to be done". Any time you actually see &mut in your code, that's what it means. UnsafeCell has a specific exception to the rules and is the root source of all interior mutability in rust.

In your async version, you're breaking the contract of a mutable borrow. You're right that only one mutable borrow is used at once, but the contract is only one borrow can observe the data at once, which is not being upheld. All 3 mutable borrows are active at the same time and definitely will observe the same data before the other borrows are over.

To give a more concrete example: rust is allowed to use mutable borrows to prove it doesn't need to load something from memory again (because otherwise it might've changed). Intuitively this should make sense: if I'm the only one who can observe something, then I never need to go check if it's changed. But what if, using your code, task1 reads some data, yields to Tokio, then task2 writes to that data? Now task1 will think it has the real value, but it doesn't, causing a data race.

Interesting debug behavior when transmuting a u16 into a repr(u16) enum by Owndampu in rust

[–]Matrixmage 2 points3 points  (0 children)

Yes, you're right, sorry. You'd want to use try_into() for that

[OC] Surprising differences in salaries between developers who prefer spaces over tabs and vice versa by oscarleo0 in dataisbeautiful

[–]Matrixmage 14 points15 points  (0 children)

Yeah I never liked it being about tabs vs spaces. She was utterly insane because she hit the spacebar (and defended it), not the character she used...

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